间伐后混交不同比例亮叶桦和毛竹对杉木生长的影响

Effects of Mixed Betula luminifera and Phyllostachys edulis with Different Proportions on the Growth of Cunninghamia lanceolata after Thinning

科学合理的混交能够恢复土壤地力,提高林分生产力,改善低质低效林,实现对杉木人工林的科学高效经营。通过对杉木人工林进行抚育间伐,以不同混交比例营造杉木-亮叶桦(1杉1桦、2杉1桦、3杉1桦)和杉木-毛竹(1杉1毛、2杉1毛、3杉1毛)混交林,探究混交对杉木个体生长特征和功能性状的影响。结果表明:1)与纯林相比,混交增加了林木竞争强度;杉木与亮叶桦混交时的林木竞争强度小于与毛竹混交。2)杉木与亮叶桦、毛竹混交均提高了杉木的叶面积指数。3)随杉木保留密度的增加,土壤中速效氮、有效磷和有机质含量随之下降;相比纯林,混交使土壤速效氮含量下降,但提高了土壤有效磷含量。4)杉木单株材积随杉木保留密度的增加而下降,林分蓄积反之。杉木-亮叶桦、杉木-毛竹混交林中,杉木单株材积和林分蓄积均高于自身纯林;杉木-亮叶桦混交林中杉木单株材积和林分蓄积同样大于杉木-毛竹混交林。5)Hegyi竞争指数与杉木单株材积呈极显著负相关(P<0.01);杉木单株材积与叶面积呈显著正相关(P<0.05);有效磷与单株材积和林分蓄积呈极显著正相关(P<0.01),土壤有机质含量与林分蓄积呈显著正相关(P<0.05)。综上,杉木-亮叶桦混交林在各方面要优于杉木-毛竹混交林;且杉木与亮叶桦混交比为1∶1时,对杉木单株生长促进效果最佳,有利于杉木大径材培育,促进杉木林分质量的提高;同时应兼顾林分产量,杉木与亮叶桦混交比为3∶1时,其杉木林分蓄积实现最大化。

Scientifically reasonable mixed planting can restore soil fertility, enhance forest productivity, improve low-quality and low-efficiency forests, and achieve scientifically efficient management of Cunninghamia lanceolata plantations.By conducting forest thinning in Cunninghamia lanceolata plantations, mixed forests can be created with different proportions of Cunninghamia lanceolata and other species such as Betula luminifera or Phyllostachys edulis.This includes combinations with ratios of Cunninghamia lanceolata to Betula luminifera or Betula luminifera at 1 ∶1,2 ∶1,and 3 ∶1,respectively.The objective is to investigate the effects of mixed planting on the growth characteristics and functional traits of Cunninghamia lanceolata individuals.The results indicate that: 1)Compared to pure forests, mixed planting increases the intensity of competition among trees.Additionally, the competition intensity between Cunninghamia lanceolata and Betula luminifera in mixed forests is lower than that between Cunninghamia lanceolata and Phyllostachys edulis.2)Mixed planting of Cunninghamia lanceolata with Betula luminifera and Phyllostachys edulis both increase the leaf area index(LAI)of Cunninghamia lanceolata.3)With the increase in Cunninghamia lanceolata retention density, the contents of available nitrogen, available phosphorus, and organic matter in the soil decrease.Compared to pure forests, mixed planting leads to a decrease of available nitrogen content in the soil but an increase in available phosphorus.4)As the retention density of Cunninghamia lanceolata increases, the individual tree volume of Cunninghamia lanceolata decreases, while the total stand volume increases in contrast.In Cunninghamia lanceolata mixed forests with Betula luminifera and Phyllostachys edulis,both the individual tree volume and the stand volume of Cunninghamia lanceolata are higher than those in pure forests of Cunninghamia lanceolata alone.In Cunninghamia lanceolata mixed forests with Betula luminifera,the individual tree volume and stand volume of Cunninghamia lanceolata are similarly greater than those in mixed forests with Phyllostachys edulis.5)The Hegyi competition index shows a highly significant negative correlation with the individual volume of Cunninghamia lanceolata(P<0.01);the individual volume of Cunninghamia lanceolata is significantly positively correlated with leaf area(P<0.05);available phosphorus is highly significantly positively correlated with individual volume and stand volume(P<0.01),and soil organic matter content is significantly positively correlated with stand volume(P<0.05).Based on the above findings, Cunninghamia lanceolata mixed forests with Betula luminifera are superior to those with Phyllostachys edulis in various aspects.Additionally, when the ratio of Cunninghamia lanceolata to Betula luminifera is 1 ∶1,it has the best promoting effect on the individual growth of Cunninghamia lanceolata,which is beneficial for cultivating large-diameter Cunninghamia lanceolata and improving stand quality.At the same time, attention should be paid to stand yield.When the ratio of Cunninghamia lanceolata to Betula luminifera is 3 ∶1,the stand volume of Cunninghamia lanceolata is maximized.